METHOD AND SYSTEM FOR CHARGING A MOTOR VEHICLE BATTERY

Abstract

The present development relates to a system and a method for charging a battery (20) of a motor vehicle (1), which can be electrically coupled to an external network (12) via an on-board charger (28), and wherein the battery (20) and / or the on-board charger (28) are designed to provide an electrical charging capacity for the network (12) and can be operated selectively in a pure charging mode or in a network buffer mode, comprising the steps: - selectively receiving a mains charge (32) to be delivered from the mains (12) in the battery (20) and / or selectively delivering a mains charge (34) requested by the mains (12) from the battery (20) in the mains buffer mode, in each case while maintaining a predetermined minimum mains charge level (36) and a predetermined maximum mains charge level (38) of the battery (20), and - at least partially charging the battery (20) by raising the predetermined minimum mains charge level (36) to a raised minimum mains charge level (36') during operation in the mains buffer mode.

Description

Technical area

[0001] The present development relates to a method and a system for charging a battery of a motor vehicle and to a motor vehicle equipped with such a system. background

[0002] Batteries from purely electric vehicles or hybrid vehicles are generally suitable for electrical connection to the existing power grid. Various approaches exist to make the storage capacity of such vehicle batteries usable for the power grid or various local electrical networks. Initial solutions are being discussed under the terms Vehicle to Grid (V2G) or Vehicle to X (V2X).

[0003] The capacity of a motor vehicle battery can be utilized, in particular, at times when the motor vehicle is not in use and, in particular, during periods when the motor vehicle is to be or is planned to be used at a predetermined later time. For example, the motor vehicle battery can be made available to a power grid, particularly at night, in order to absorb surplus power from the grid or to supply electrical charge stored in the motor vehicle battery to the grid as needed. This can be a local power grid, such as that of a building or an industrial plant, or a regional or supra-regional power grid, such as that of an electricity supplier.

[0004] When driving a motor vehicle, it is desirable for the user if the motor vehicle has a maximum range at the start of the journey due to its electrical coupling, for example with a stationary charging infrastructure, i.e. that the battery of the motor vehicle has, if possible, its maximum charge level at the start of the journey.

[0005] Motor vehicles or motor vehicle batteries can be operated in a grid buffer mode, in which the motor vehicle battery is electrically coupled to an external grid and, in grid buffer mode, can either provide a grid charge requested by the grid or accept a grid charge delivered by the grid. Accepting and / or delivering such grid charges in grid buffer mode may entail remuneration for the owner of the motor vehicle or battery. This can apply both to the grid charge delivered from the grid to the motor vehicle battery and to the grid charge requested from the grid and delivered by the battery to the grid.

[0006] However, if the driver of the vehicle wishes to fully charge the vehicle battery at a predetermined time, it may be necessary for the battery or an on-board charger electrically coupled to the battery to switch from grid buffer mode to a pure charging mode, in which the energy generally provided by the external grid is used predominantly or exclusively to fully charge the vehicle battery. Of course, the vehicle user must pay the grid operator a corresponding fee for this.

[0007] Switching from the grid buffer mode to the pure charging mode is particularly necessary if, according to user specifications, the vehicle battery is to be fully charged at a given time.

[0008] If and as long as the vehicle's battery or on-board charger is in grid buffer mode, the actual battery state of charge can vary between a specified maximum and minimum grid charge level. If switching from grid buffer mode to pure charging mode occurs when the battery state of charge is close to the minimum grid charge level, the end user must supply a comparatively large amount of electrical power from the external grid to the battery, which entails correspondingly high costs.

[0009] However, if switching from the grid buffer mode to pure charging mode occurs at a time when the battery has a charge level close to its maximum grid charge level, the total amount of energy that has to be supplied externally to the battery via the grid until the maximum charge level is reached may be significantly lower, which would entail correspondingly lower costs.

[0010] However, as long as the battery or on-board charger is in grid buffer mode, the end user has no influence on the actual current state of charge of the vehicle's battery. This state of charge correlates with the grid's requirements over time.

[0011] Against this background, the objective of this further development is to provide an improved method for charging a battery of a motor vehicle and a correspondingly improved system for charging the battery, which is associated with the lowest possible costs for the end user for charging the battery and which at the same time enables a sufficiently high level of user comfort, for example for driving the motor vehicle with the battery as fully charged as possible. Advantageous designs

[0012] This object is achieved by a method, a system and a motor vehicle according to the features of the independent patent claims, wherein advantageous embodiments are each the subject of dependent patent claims.

[0013] In a first aspect, a method for charging a battery of a motor vehicle is provided. The battery can be electrically coupled to an external network via an on-board charger of the motor vehicle. The battery and / or the on-board charger is / are designed to provide an electrical charging capacity for the network and can be operated optionally in a pure charging mode or in a network buffer mode.

[0014] In pure charging mode, the on-board charger draws exclusively electrical power or electrical energy from the external grid and uses this drawn electrical energy to charge the battery. In grid buffer mode, however, at least partial charging and discharging of the battery can occur within specified limits, namely within specified grid charge levels, specifically between a minimum grid charge level and a maximum grid charge level. In this way, the vehicle's battery in grid buffer mode can meet the corresponding charging and / or discharging requirements of the grid, which results in appropriate compensation for the vehicle user or proves to be economically advantageous for the vehicle user.

[0015] The method for charging the motor vehicle battery in grid buffer mode comprises selectively receiving a grid charge to be supplied from the grid into the battery and / or selectively supplying a grid charge requested from the grid from the battery. During operation in grid buffer mode, the on-board charger ensures that the current charge level of the battery remains within specified limits, namely between a minimum specified grid charge level and a specified maximum grid charge level.

[0016] This means that during operation in grid buffer mode, the minimum grid charge level cannot be undercut and the maximum grid charge level cannot be exceeded. This ensures that only a portion of the total capacity provided by the vehicle battery is made available to the external grid, allowing the end user to disconnect from the grid at any time and, for example, start a journey with the vehicle.

[0017] The battery may not be at its maximum charge level. However, the minimum mains charge level should be sufficient for driving a certain distance. If necessary, the user can individually set the maximum and minimum mains charge levels.

[0018] To at least partially charge the battery or even fully charge it in grid buffer mode, the specified minimum grid charge level can be raised or increased to a higher minimum grid charge level during operation in grid buffer mode. In this way, it can be achieved more or less inherently or automatically that the battery releases no or only a small amount of electrical charge to the grid even during operation in grid buffer mode, but conversely, absorbs more electrical energy or electrical charge, provided the grid provides sufficient power.

[0019] In this way, namely by gradually or successively or even continuously increasing or raising the specified minimum mains charge level, it can be achieved that, for example, when switching from the mains buffer mode to the pure charging mode of the on-board charger or the battery, the battery now has a significantly higher charge level compared to the initial situation, so that the end user only has to supply a comparatively small electrical charge to the battery to fully charge the battery, which can have an extremely positive effect from an economic point of view.

[0020] According to a further embodiment of the method, the delivery of a grid charge requested from the grid to the grid is suppressed if and as soon as the raised minimum grid charge level is equal to or greater than the actual charge level of the battery. In this way, it is effectively prevented that the battery is further discharged or discharged to a level below the raised minimum grid charge level when a grid charge is requested. Discharging of the battery below the minimum grid charge level is generally prevented if necessary, so that by gradually or stepwise raising the minimum grid charge level, a gradual charging or a gradual increase in the actual charge level of the battery can be achieved.

[0021] According to a further embodiment of the method, a mains charge delivered from the mains is absorbed by the battery in mains buffer mode until the specified maximum mains charge level of the battery is reached. Only when the specified maximum mains charge level of the battery is reached can further absorption of electrical power from the mains to the battery be prevented, effectively preventing the battery from reaching an excessively high charge level too early, which could potentially be harmful or detrimental to the long-term operation of the battery.

[0022] According to a further embodiment, the specified maximum grid charge level is increased during operation in grid buffer mode to at least partially charge the battery. This can involve a gradual or even linear increase in the maximum grid charge level during operation in grid buffer mode. In this way, the upper limit or upper barrier for the actual battery charge level can be raised, if necessary, to the maximum permissible battery charge level, in particular to minimize any difference to full battery charging when switching from grid buffer mode to pure charging mode.

[0023] According to a further embodiment, an increase in the specified minimum grid charge level and / or an increase in the specified maximum grid charge level of the battery during operation in grid buffer mode is provided according to a specified temporal function, or the increase is carried out based on a specified temporal function. The temporal function can, for example, be stored in the on-board charger. It can, for example, specify a rate of change of the minimum grid charge level and the maximum grid charge level over time.

[0024] The gradient or the temporal rate of change of the minimum grid state of charge and / or the maximum grid state of charge may depend on or be adapted to external factors, such as the available grid power, the absolute values ​​of the specified minimum and / or maximum grid state of charge as well as user specifications regarding a time specification for fully charging the vehicle battery.

[0025] According to a further embodiment of the method, the battery is charged to the specified maximum charge level or can be charged accordingly as a result of switching from the grid buffer mode to the pure charging mode by supplying a battery charge provided by the grid. In this way, it can be achieved that at a specified time or after the expiration of a specified time interval, e.g., specified by the user, the battery of the motor vehicle has a maximum charge level, thus allowing the motor vehicle to achieve a maximum range.

[0026] In a further aspect, a system for charging a motor vehicle battery is also provided. The system comprises the aforementioned motor vehicle battery and an on-board charger, which is electrically coupled to the battery and can optionally be electrically coupled to an external network. The on-board charger can be coupled, in particular, to a stationary network, such as a local electrical network of a property or to a regional or supra-regional network of an energy supplier.

[0027] The battery and / or the on-board charger is / are designed to provide an electrical charging capacity for the grid and can be operated either in a pure charging mode or in a grid buffer mode. In particular, the on-board charger can be configured to selectively supply a grid charge to be delivered by the grid to the battery in grid buffer mode and / or to selectively transfer a grid charge requested from the grid from the battery to the grid. In this case, and as long as the system is in grid buffer mode, the actual battery charge level is maintained between a predefined minimum grid charge level and a predefined maximum grid charge level of the battery.

[0028] This means that the operation of the battery as well as at least partial charging or partial discharging in accordance with the requirements of the grid takes place in compliance with a specified minimum grid charge level and a specified maximum grid charge level of the battery.

[0029] In grid buffer mode, the on-board charger is further configured to at least partially charge the battery by raising the specified minimum grid charge level to a raised minimum grid charge level. It is provided that during operation in grid buffer mode, in which the battery is configured both to deliver and receive electrical charge, thus exchanging electrical power with the grid, the minimum permissible grid charge level of the battery is raised gradually or successively, if necessary continuously over time, in order to ensure that the actual charge level of the battery increases continuously or gradually, namely at least during phases in which the grid intends to supply the battery with a grid charge.

[0030] In other situations where the grid requests a grid charge from the battery, such a request can be denied, or at least throttled or suppressed, so that the battery is at least charged during grid buffer mode, but only discharged to a significantly lesser extent. In grid buffer mode, the end user can receive a fee from the grid operator for both charging and discharging their vehicle battery, or such charging or discharging proves to be extremely economically advantageous for the battery or vehicle operator.

[0031] When subsequently switching from grid buffer mode to pure charging mode, for example, to fully charge the vehicle battery, it can be assumed that the actual state of charge of the battery is significantly higher than its initial state, so that the end user has to purchase far less electrical charge to fully charge the battery. According to a further embodiment, the on-board charger is designed to suppress the delivery of a grid charge requested from the grid to the grid in grid buffer mode if and as soon as the increased minimum grid charge level is equal to or greater than the actual state of charge of the battery.

[0032] In particular, the system described here is intended for the practical implementation or operation of the previously described method for charging a motor vehicle battery. In this respect, all features, properties, and advantages previously described for the method also apply equally to the system for charging the motor vehicle battery; and vice versa.

[0033] In light of all of the above and in a further aspect, the present development finally relates to a motor vehicle, such as a passenger car, a small van, a transporter, or a bus, equipped with a system for charging a battery described above. The motor vehicle typically has an electric drive, which can be at least partially powered by the battery. Optionally, the motor vehicle has a fuel cell and / or a similar power generation device on board, for example, to also charge the battery during operation of the motor vehicle. Short description of the characters

[0034] Further objects, features, and advantageous applications of the method and system for charging a motor vehicle battery are explained with reference to the following drawings. Fig. 1 a schematic representation of a motor vehicle, Fig. 2 a block diagram of a charging system of the motor vehicle, Fig. 3 a diagram of the battery charge level over time, Fig. 4 another diagram illustrating the battery charge level over time and Fig. 5 a flowchart of the method for charging the battery of the motor vehicle. Detailed description

[0035] The Fig. The motor vehicle 1 shown in FIG. 1 has a self-supporting vehicle body 2 and an interior 3 functioning as a passenger compartment. The motor vehicle 1 further has a drive 4, which is typically designed as an electric drive. The electric drive 4 can be powered in particular by a battery 20, for example in the form of a high-voltage battery.

[0036] In Fig. 2 shows a schematic representation of a charging system 10 of the motor vehicle 1. The charging system 10 has the aforementioned battery 20, which can be electrically coupled optionally to an external network 12 via an on-board charger 28. The battery 20 is further connected to a high-voltage system 26 of the motor vehicle. The high-voltage system 26 includes, for example, the drive 4 of the motor vehicle 1 and / or other high-voltage components. The battery 20 can further be coupled to a 12-volt on-board network 24 or low-voltage system of the motor vehicle 1 via a converter 22, for example, via a DC / DC converter. The on-board network 24 can include, for example, the on-board electronics of the motor vehicle 1 and electrical consumers coupled thereto or controlled thereby.

[0037] In Fig. Figure 3 shows an example of the operation of the charging system 10. The state of charge (SoC) of the battery 35 is shown vertically. A time axis is shown horizontally.

[0038] In a time interval T0 to T1, the battery 20 is charged, which has a minimum permissible state of charge at time T0. Charging of the battery 20 can be achieved, in particular, by electrical coupling to the external grid 12. During the period T0 to T1, the grid provides a chargeable battery charge 30, since during this period T0 to T1 the charging system 10, thus the on-board charger 28 and / or the battery 20, is in a pure charging mode.

[0039] At time T1, the charging system 10 switches to a grid buffer mode. In the grid buffer mode, electrical charge can be selectively exchanged between the on-board charger 28 and the external grid 12 depending on the requirement 39 of the grid 12. A grid charge 34 can be delivered from the battery 20 to the grid 12 via the on-board charger 28, either upon request 39 of the grid 12 or at other times. Likewise, and again upon request 39 of the grid 12, excess electrical energy from the grid 12 can be delivered to the battery 20 in the form of a grid charge 32 via the on-board charger 28.

[0040] Supplying a mains charge 32 from the mains 12 to the battery 20 leads to an increase in the actual state of charge 35 of the battery. A mains charge 34 requested from the mains, which is provided by the battery 20, leads to a decrease in the state of charge 35 of the battery 20, at least in some areas.

[0041] As is particularly evident in the period between T1 and T3, there is an alternating supply and discharge of network charges 32, 34, thus a lively exchange with the network 12. In both diagrams of the Fig. 3 and Fig. 4, a user specification exists such that at a time T4 the battery 20 has a maximum state of charge 40, so that the end user can move or operate the vehicle with a maximum range at time T4.

[0042] In the Fig. 3 and Fig. 4, at time T3, the charging system 10 is switched from the mains buffer mode to the pure charging mode in order to fully charge the battery 20. At time T3 according to the example according to Fig. 3, the actual state of charge 35 is within the limits specified by the minimum grid state of charge 36 and the maximum grid state of charge 38. At time T3, it is even below an average grid state of charge 37, or a target grid state of charge 37. To reach the maximum state of charge 40 at time T4, a comparatively large charge E1 must therefore be supplied to the battery 20, which the user may have to purchase from the grid operator for a fee.

[0043] According to the diagram Fig. 4 it is now provided that during the grid buffer mode, namely already at a time T2 preceding the time T3 for at least partially charging the battery 20, the predetermined minimum grid charge level 36 is successively increased, in the present example linearly over time, to a raised minimum grid charge level 36' during operation in the grid buffer mode.

[0044] This results in the system 10 progressively preventing the discharge of a grid charge 34 to the grid 12 but always ensuring that the grid charge 32 is removed from the grid 12. This results in the actual charge level 35 being gradually increased in the time interval between times T2 to T3, and discharging the battery or providing grid power 34 to be delivered to the grid is still permitted but is progressively prevented or restricted by progressively increasing the minimum grid charge level 36'.

[0045] At the same time or at a different time than the increase in the minimum grid charge level 36, the maximum grid charge level 38' is also increased, so that the average grid charge level 37' or a target grid charge level 37' is also gradually increased.

[0046] At time T3, the average network charge level 37' can be seen in the diagram of the Fig. 4 approximately coincide with the maximum state of charge 40 of the battery 20. For long-term operation of the battery 20 and to avoid premature battery aging, it is desirable if the maximum state of charge 40 is actually only reached at the specified time T4.

[0047] By comparing the Fig. 3 and Fig. 4 it is immediately apparent that at time T3 according to the procedure of Fig. 4 to supply a significantly lower amount of electrical charge E2 to the battery from the grid 12 in order to achieve the maximum charge level 40 of the battery 20. During the grid buffer mode, the supply or supply of grid charge 32, 34 can be carried out comparatively inexpensively or even on the basis of remuneration.

[0048] Only the purchase of an additional battery charge 30, for example to fully charge the battery between times T3 and T4, must be subject to payment.

[0049] By using the Fig. 4 described increase of the specified minimum network charge level 36' and the specified maximum network charge level 38', a significantly higher charge level 35 can be achieved at time T3 than is possible according to the method according to Fig. 3 is the case. The result is a significant saving in the cost of charging the battery 20 without having to accept any loss in vehicle range or user comfort.

[0050] In Fig.Finally, Figure 5 shows a flowchart which further illustrates the method for charging the battery. In a first step 100, the battery is charged in pure charging mode, approximately between times T0 to T1. Following this, in step 102, the battery switches to grid buffer mode. As a result, while maintaining the predefined minimum grid charge level 36 and the predefined maximum grid charge level 38 of the battery 20, the battery 20 can either absorb an excess grid charge 32 from the grid 12 or serve a request 39 from the grid 12 and deliver a corresponding grid charge 34 to the grid 12. This buffering of electrical charges by means of the battery 20 takes place within the predefined minimum and maximum grid charge levels.

[0051] In step 104, the battery 20 is at least partially charged in the grid buffer mode by raising the predetermined minimum grid charge level 36 to a raised minimum grid charge level 36', as is provided in particular in the period between T2 and T3. At time T3 and in step 106, a switchover from the grid buffer mode to the pure charging mode then occurs in order to fully charge the battery 20 by supplying a battery charge 30 from the grid 12.

[0052] The illustrated embodiments merely show possible configurations of the development, for which numerous further variants are conceivable within the scope of the development. The exemplary embodiments shown are in no way to be interpreted as limiting the scope, applicability, or configuration options of the development. This description merely shows the person skilled in the art one or several possible implementations of an exemplary embodiment. Thus, a wide variety of modifications can be made to the function and arrangement of the described elements without departing from the scope of protection defined by the following claims or their equivalents. List of reference symbols 1 motor vehicle 2 Motor vehicle body 3 Interior 4 Drive 10 Charging system 12 Network 20 Battery 22 converters 24 low-voltage system 26 high-voltage system 28 On-board charger 30 battery charges 32 Mains charging 34 Mains charging 35 Charge level 36 minimum mains charge level 37 average mains charge level 38 maximum mains charge level 39 Network requirement 40 maximum charge level

Claims

[1] Method for charging a battery (20) of a motor vehicle (1), which can be electrically coupled to an external network (12) via an on-board charger (28), and wherein the battery (20) and / or the on-board charger (28) are designed to provide an electrical charging capacity for the network (12) and can be operated selectively in a pure charging mode or in a network buffer mode, comprising the steps: - selectively receiving a mains charge (32) to be delivered from the mains (12) in the battery (20) and / or selectively delivering a mains charge (34) requested by the mains (12) from the battery (20) in the mains buffer mode, in each case while maintaining a predetermined minimum mains charge level (36) and a predetermined maximum mains charge level (38) of the battery (20), and - at least partially charging the battery (20) by raising the predetermined minimum mains charge level (36) to a raised minimum mains charge level (36') during operation in the mains buffer mode. [2] Method according to claim 1, wherein delivery of a network charge (34) requested by the network (12) to the network (12) is suppressed if and as soon as the raised minimum network charge level (36') is equal to or greater than the actual charge level (35) of the battery (20). [3] Method according to claim 1 or 2, wherein a mains charge (32) to be delivered from the mains (12) is received in the mains buffer mode until the predetermined maximum mains charge state (38) of the battery (20) is reached. [4] Method according to one of the preceding claims, wherein for at least partially charging the battery (20), the predetermined maximum network charge state (38') is increased during operation in the network buffer mode. [5] Method according to one of the preceding claims, wherein an increase in the predetermined minimum network charge level (36) and / or an increase in the predetermined maximum network charge level (38) of the battery (20) occurs during operation in the network buffer mode according to a predetermined time function. [6] Method according to one of the preceding claims, wherein the increase of the predetermined minimum network charge level (36) and / or the maximum network charge level (38) begins on the basis of a time specification and / or on the basis of a predetermined maximum charge level (40) of the battery (20). [7] Method according to one of the preceding claims, wherein the battery (20) is charged to the predetermined maximum charge state (40) as a result of switching from the mains buffer mode to the pure charging mode by supplying a battery charge (30) provided by the mains (12). [8] System (10) for charging a battery (20) of a motor vehicle (1), comprising: - the battery (20), - an on-board charger (28) which is electrically coupled to the battery (20) and which can optionally be electrically coupled to an external network (12), - wherein the battery (20) and / or the on-board charger (28) are designed to provide an electrical charging capacity for the network (12) and can be operated selectively in a pure charging mode or in a network buffer mode, and wherein the on-board charger (28) is designed to - in the mains buffer mode, optionally supplying a mains charge (32) to be delivered by the mains (12) to the battery (20) and / or optionally discharging a mains charge (34) requested by the mains (12) from the battery (20) to the mains, in each case while maintaining a predetermined minimum mains charge level (36) and a predetermined maximum mains charge level (38) of the battery (20), and - in the mains buffer mode, to charge the battery (20) at least partially by raising the predetermined minimum mains charge level (36) to a raised minimum mains charge level (36'). [9] System (10) according to claim 8, wherein the on-board charger (28) is designed to suppress, in the network buffer mode, delivery of a network charge (34) requested by the network (12) to the network (12) if and as soon as the raised minimum network charge level (36') is equal to or greater than the actual charge level (35) of the battery (20). [10] Motor vehicle (1) with a system according to one of the preceding claims 8 or 9.

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